Ralph, The "understanding" Gilles just expresses matches my own.
The issue that the OP observed on an ARM/Linux system (and I was able to reproduce on Linux w/ any arch) is that when the LO interface is missing Linux is unable to pass loopback messages sent on ANY interface. The oob_tcp code was trying to connect to a 172.18.0.x address when I reproduced it. In summary: For LINUX the lack of a loopback interface (selected or not) prevents local connection. For NON-LINUX the lack of a loopback interface MAKES NO DIFFERENCE. So, I think Gilles's version is correct, but that making the logic (at least the reporting) conditional on Linux might be an improvement. Since this is a warning, it might be better to remove from 1.8 until we have more certainty about where/when it matters. I don't think users will appreciate a "cry wolf" release. -Paul On Thu, Dec 11, 2014 at 9:01 PM, Gilles Gouaillardet < gilles.gouaillar...@iferc.org> wrote: > Ralph, > > here is my understanding of what happens on Linux : > > lo: 127.0.0.1/8 > eth0: 192.168.122.101/24 > > mpirun --mca orte_oob_tcp_if_include eth0 ... > > so the mpi task tries to contact orted/mpirun on 192.168.0.1/24 > > that works just fine if the loopback interface is active, > and that hangs if there is no loopback interface. > > > imho that is a linux oddity, and OMPI has nothing to do with it > > Cheers, > > Gilles > > [root@slurm1 ~]# ping -c 3 192.168.122.101 > PING 192.168.122.101 (192.168.122.101) 56(84) bytes of data. > 64 bytes from 192.168.122.101: icmp_seq=1 ttl=64 time=0.013 ms > 64 bytes from 192.168.122.101: icmp_seq=2 ttl=64 time=0.009 ms > 64 bytes from 192.168.122.101: icmp_seq=3 ttl=64 time=0.011 ms > > --- 192.168.122.101 ping statistics --- > 3 packets transmitted, 3 received, 0% packet loss, time 1999ms > rtt min/avg/max/mdev = 0.009/0.011/0.013/0.001 ms > > > > [root@slurm1 ~]# ifdown lo > [root@slurm1 ~]# ping -c 3 192.168.122.101 > PING 192.168.122.101 (192.168.122.101) 56(84) bytes of data. > > --- 192.168.122.101 ping statistics --- > 3 packets transmitted, 0 received, 100% packet loss, time 11999ms > > > > On 2014/12/12 13:54, Ralph Castain wrote: > > I honestly think it has to be a selected interface, Gilles, else we will fail > to connect. > > > On Dec 11, 2014, at 8:26 PM, Gilles Gouaillardet > <gilles.gouaillar...@iferc.org> <gilles.gouaillar...@iferc.org> wrote: > > Paul, > > about the five warnings : > can you confirm you are running mpirun *not* on n15 nor n16 ? > if my guess is correct, then you can get up to 5 warnings : mpirun + 2 orted > + 2 mpi tasks > > do you have any oob_tcp_if_include or oob_tcp_if_exclude settings in your > openmpi-mca-params.conf ? > > here is attached a patch to fix this issue. > what we really want is test there is a loopback interface, period. > the current code (my bad for not having reviewed in a timely manner) seems to > check > there is a *selected* loopback interface. > > Cheers, > > Gilles > > On 2014/12/12 13:15, Paul Hargrove wrote: > > Ralph, > > Sorry to be the bearer of more bad news. > The "good" news is I've seen the new warning regarding the lack of a > loopback interface. > The BAD news is that it is occurring on a Linux cluster that I'ver verified > DOES have 'lo' configured on the front-end and compute nodes (UP and > RUNNING according to ifconfig). > > Though run with "-np 2" the warning appears FIVE times. > ADDITIONALLY, there is a SEGV at exit! > > Unfortunately, despite configuring with --enable-debug, I didn't get line > numbers from the core (and there was no backtrace printed). > > All of this appears below (and no, "-mca mtl psm" is not a typo or a joke). > > Let me know what tracing flags to apply to gather the info needed to debug > this. > > -Paul > > > $ mpirun -mca btl sm,self -np 2 -host n15,n16 -mca mtl psm examples/ring_c > -------------------------------------------------------------------------- > WARNING: No loopback interface was found. This can cause problems > when we spawn processes as they are likely to be unable to connect > back to their host daemon. Sadly, it may take awhile for the connect > attempt to fail, so you may experience a significant hang time. > > You may wish to ctrl-c out of your job and activate loopback support > on at least one interface before trying again. > > -------------------------------------------------------------------------- > [... above message FOUR more times ...] > Process 1 exiting > Process 0 sending 10 to 1, tag 201 (2 processes in ring) > Process 0 sent to 1 > Process 0 decremented value: 9 > Process 0 decremented value: 8 > Process 0 decremented value: 7 > Process 0 decremented value: 6 > Process 0 decremented value: 5 > Process 0 decremented value: 4 > Process 0 decremented value: 3 > Process 0 decremented value: 2 > Process 0 decremented value: 1 > Process 0 decremented value: 0 > Process 0 exiting > -------------------------------------------------------------------------- > mpirun noticed that process rank 0 with PID 0 on node n15 exited on signal > 11 (Segmentation fault). > -------------------------------------------------------------------------- > > $ /sbin/ifconfig lo > lo Link encap:Local Loopback > inet addr:127.0.0.1 Mask:255.0.0.0 > inet6 addr: ::1/128 Scope:Host > UP LOOPBACK RUNNING MTU:16436 Metric:1 > RX packets:481228 errors:0 dropped:0 overruns:0 frame:0 > TX packets:481228 errors:0 dropped:0 overruns:0 carrier:0 > collisions:0 txqueuelen:0 > RX bytes:81039065 (77.2 MiB) TX bytes:81039065 (77.2 MiB) > > $ ssh n15 /sbin/ifconfig lo > lo Link encap:Local Loopback > inet addr:127.0.0.1 Mask:255.0.0.0 > inet6 addr: ::1/128 Scope:Host > UP LOOPBACK RUNNING MTU:16436 Metric:1 > RX packets:24885 errors:0 dropped:0 overruns:0 frame:0 > TX packets:24885 errors:0 dropped:0 overruns:0 carrier:0 > collisions:0 txqueuelen:0 > RX bytes:1509940 (1.4 MiB) TX bytes:1509940 (1.4 MiB) > > $ ssh n16 /sbin/ifconfig lo > lo Link encap:Local Loopback > inet addr:127.0.0.1 Mask:255.0.0.0 > inet6 addr: ::1/128 Scope:Host > UP LOOPBACK RUNNING MTU:16436 Metric:1 > RX packets:24938 errors:0 dropped:0 overruns:0 frame:0 > TX packets:24938 errors:0 dropped:0 overruns:0 carrier:0 > collisions:0 txqueuelen:0 > RX bytes:1543408 (1.4 MiB) TX bytes:1543408 (1.4 MiB) > > $ gdb examples/ring_c core.29728 > [...] > (gdb) where > #0 0x0000002a97a19980 in ?? () > #1 <signal handler called> > #2 0x0000003a6d40607c in _Unwind_FindEnclosingFunction () from > /lib64/libgcc_s.so.1 > #3 0x0000003a6d406b57 in _Unwind_RaiseException () from > /lib64/libgcc_s.so.1 > #4 0x0000003a6d406c4c in _Unwind_ForcedUnwind () from /lib64/libgcc_s.so.1 > #5 0x0000003a6c30ac50 in __pthread_unwind () from > /lib64/tls/libpthread.so.0 > #6 0x0000003a6c305202 in sigcancel_handler () from > /lib64/tls/libpthread.so.0 > #7 <signal handler called> > #8 0x0000003a6b6bd9a2 in poll () from /lib64/tls/libc.so.6 > #9 0x0000002a978f8f7d in ?? () > #10 0x002000010000000e in ?? () > #11 0x0000000000000000 in ?? () > > > > _______________________________________________ > devel mailing list > de...@open-mpi.org <mailto:de...@open-mpi.org> <de...@open-mpi.org> > Subscription: http://www.open-mpi.org/mailman/listinfo.cgi/devel > <http://www.open-mpi.org/mailman/listinfo.cgi/devel> > <http://www.open-mpi.org/mailman/listinfo.cgi/devel> > Link to this post: > http://www.open-mpi.org/community/lists/devel/2014/12/16525.php > <http://www.open-mpi.org/community/lists/devel/2014/12/16525.php> > <http://www.open-mpi.org/community/lists/devel/2014/12/16525.php> > > <loopback.diff>_______________________________________________ > devel mailing listde...@open-mpi.org > Subscription: http://www.open-mpi.org/mailman/listinfo.cgi/devel > Link to this post: > http://www.open-mpi.org/community/lists/devel/2014/12/16526.php > > > > _______________________________________________ > devel mailing listde...@open-mpi.org > Subscription: http://www.open-mpi.org/mailman/listinfo.cgi/devel > Link to this post: > http://www.open-mpi.org/community/lists/devel/2014/12/16527.php > > > > _______________________________________________ > devel mailing list > de...@open-mpi.org > Subscription: http://www.open-mpi.org/mailman/listinfo.cgi/devel > Link to this post: > http://www.open-mpi.org/community/lists/devel/2014/12/16529.php > -- Paul H. Hargrove phhargr...@lbl.gov Computer Languages & Systems Software (CLaSS) Group Computer Science Department Tel: +1-510-495-2352 Lawrence Berkeley National Laboratory Fax: +1-510-486-6900
